The catechol-O-methyltransferase polymorphism: relations to the tonic-phasic dopamine hypothesis and neuropsychiatric phenotypes

Association between executive functions and COMT Val108/158Met polymorphism among healthy younger and older adults: A preliminary study

BACKGROUND AND OBJECTIVES

Genetic variability in the dopaminergic system could contribute to age-related impairments in executive control. In this study, we examined whether genetic polymorphism for catechol-O-methyltransferase (COMT Val158Met) is related to performance on updating, shifting and inhibition tasks.

METHODS

We administered a battery of executive tasks assessing updating, shifting and inhibition functions to 45 older and 55 younger healthy participants, and created composite z-scores associated to each function. Six groups were created based on genetic alleles (Val/Val, Val/Met, Met/Met) derived from the COMT gene and age (younger, older). Age and genotype effects were assessed with t-test and ANOVA (p<0.05).

RESULTS

A lower performance was observed in the older group for the three executive processes, and more particularly for inhibition. Moreover, older participants homozygous for the Val allele have a lower performance on the inhibition composite in comparison to younger Val/Val.

CONCLUSIONS

These results confirm presence of executive performance decrease in healthy aging. With regard to genetic effect, older participants seem particularly disadvantaged when they have a lower baseline dopamine level (i.e., Val/Val homozygous) that is magnified by aging, and when the executive measure emphasize the need of stable representations (as in inhibition task requiring to maintain active the instruction to not perform an automated process).

Gray matter matters: Cognitive stability and flexibility in schizophrenia spectrum disorder

Cognitive dysfunction constitutes a core characteristic of schizophrenia spectrum disorders (SZ). Specifically, deficits in updating generative models (i.e., cognitive flexibility) and shielding against distractions (i.e., cognitive stability) are considered critical contributors to cognitive impairment in these patients. Here, we examined the structural integrity of frontostriatal networks and their associations with reduced cognitive stability and flexibility in SZ patients. In a sample of 21 patients diagnosed with SZ and 22 healthy controls, we measured gray matter volume (GMV) using structural MRI. Further, cognitive stability and flexibility were assessed using a switch-drift paradigm, quantifying the successful ignoring of distracters and detection of rule switches. Compared to controls, patients showed significantly smaller GMV in the whole brain and three predefined regions of interest: the medial prefrontal cortex (mPFC), inferior frontal gyrus (IFG), and caudate nucleus (CN). Notably, GMV in these areas positively correlated with correct rule-switch detection but not with ignoring rule-compatible drifts. Further, the volumetric differences between SZ patients and controls were statistically explainable by considering the behavioral performance in the switch-drift task. Our results indicate that morphological abnormalities in frontostriatal networks are associated with deficient flexibility in SZ patients and highlight the necessity of minimizing neurodevelopmental and progressive brain atrophy in this population.

Preliminary Evidence for a Positive Relation Between the COMT rs4680 Met/Met Genotype and Math Achievement

To identify if COMT polymorphisms interact with executive functions as predictors of math skills, we assessed 38 adolescents (mean age = 16.4 ± 0.80 years, IQ > 80) from a larger study of high-school students screened for their mathematical abilities. Adolescents were genotyped for the COMT Val158Met polymorphism (grouped as Met/Met or Val-carriers) and completed the WRAT math achievement test, working-memory, inhibitory-control, and shifting tasks. Met/Met-carriers achieved higher WRAT scores than the Val-carriers (W = 229, p = .009). Genotype group was a moderate-to-strong predictor of WRAT scores (β = 0.56 to 0.74). No genotype/executive-function interaction was detected. Our findings suggest that the rs4680 Met/Met genotype is positively associated with math achievement.

Association of SLC6A3 variants with treatment-resistant schizophrenia: a genetic association study of dopamine-related genes in schizophrenia

Background

Most genetic analyses that have attempted to identify a locus or loci that can distinguish patients with treatment-resistant schizophrenia (TRS) from those who respond to treatment (non-TRS) have failed. However, evidence from multiple studies suggests that patients with schizophrenia who respond well to antipsychotic medication have a higher dopamine (DA) state in brain synaptic clefts whereas patients with TRS do not show enhanced DA synthesis/release pathways.

Patients and methods

To examine the contribution (if any) of genetics to TRS, we conducted a genetic association analysis of DA-related genes in schizophrenia patients (TRS, n = 435; non-TRS, n = 539) and healthy controls (HC: n = 489).

Results

The distributions of the genotypes of rs3756450 and the 40-bp variable number tandem repeat on SLC6A3 differed between the TRS and non-TRS groups. Regarding rs3756450, the TRS group showed a significantly higher ratio of the A allele, whereas the non-TRS group predominantly had the G allele. The analysis of the combination of COMT and SLC6A3 yielded a significantly higher ratio of the putative low-DA type (i.e., high COMT activity + high SLC6A3 activity) in the TRS group compared to the two other groups. Patients with the low-DA type accounted for the minority of the non-TRS group and exhibited milder psychopathology.

Conclusion

The overall results suggest that (i) SLC6A3 could be involved in responsiveness to antipsychotic medication and (ii) genetic variants modulating brain DA levels may be related to the classification of TRS and non-TRS.

The Influence of Genetic Polymorphic Variability of the Catechol-O-methyltransferase Gene in a Group of Patients with a Diagnosis of Behavioural Addiction, including Personality Traits

Gambling Disorder (GD) is characterised by a harmful, enduring, and recurrent involvement in betting-related behaviours. Therefore, GD shares similar biological mechanisms and symptoms to substance use disorders (SUD). Therefore, in this study, we chose the behavioural addictions group. During the examination and recruitment to the study, it turned out that all the people undergoing treatment for gambling addiction were also addicted to amphetamines, which is consistent with the biological mechanism related to cerebral neurotransmission. The aim of the study was to investigate the association of the COMT gene polymorphism with behavioral addiction. The study group consisted of 307 participants: 107 men with gambling disorder and amphetamine dependency (mean age = 27.51, SD = 5.25) and 200 non-addicted, nor dependent, free from neuro-psychiatric disorders control group men (mean age = 20.20, SD = 4.51). Both groups were subjected to psychometric evaluation using the State-Trait Anxiety Inventory and the NEO Five-Factor Personality Inventory. Genomic DNA was extracted from venous blood following standard protocols. Determination of the rs4680 polymorphism in the COMT gene was performed using the real-time PCR technique. Statistically significant differences in the frequency of rs4680 genotypes were found in the tested sample of subjects compared with the control group (p = 0.03543). Subjects with gambling disorder and amphetamine use disorder compared to the control group obtained higher scores in the assessment of the STAI trait scale (p = 0.0019), state scale (p < 0.0000), and NEO-FFI Neuroticism scale (p < 0.0000). Significantly lower results were obtained for the NEO-FFI Agreeability scale (p < 0.0000). Additionally, a significant statistical impact of gambling disorder and amphetamine use disorder, and the COMT rs4680 genotype was demonstrated for the score of the STAI trait (p = 0.0351) and state (p = 0.0343) and the NEO-FFI Conscientiousness scale (p = 0.0018). We conclude that COMT and its polymorphic variant influence the development of addiction. Still, considering its multifactorial and polygenic nature, it should be combined with other factors such as personality.

Dopamine Modulates Effective Connectivity in Frontal Cortex

There is increasing evidence that the left lateral frontal cortex is hierarchically organized such that higher-order regions have an asymmetric top-down influence over lower order regions. However, questions remain about the underlying neuroarchitecture of this hierarchical control organization. Within the frontal cortex, dopamine plays an important role in cognitive control functions, and we hypothesized that dopamine may preferentially influence top-down connections within the lateral frontal hierarchy. Using a randomized, double-blind, within-subject design, we analyzed resting-state fMRI data of 66 healthy young participants who were scanned once each after administration of bromocriptine (a dopamine agonist with preferential affinity for D2 receptor), tolcapone (an inhibitor of catechol-O-methyltransferase), and placebo, to determine whether dopaminergic stimulation modulated effective functional connectivity between hierarchically organized frontal regions in the left hemisphere. We found that dopaminergic drugs modulated connections from the caudal middle frontal gyrus and the inferior frontal sulcus to both rostral and caudal frontal areas. In dorsal frontal regions, effectivity connectivity strength was increased, whereas in ventral frontal regions, effective connectivity strength was decreased. These findings suggest that connections within frontal cortex are differentially modulated by dopamine, which may bias the influence that frontal regions exert over each other.

The Val158Met Polymorphism in 8-Year-Old Boys and Girls Moderates the Influence of Parenting Styles on Proactive Aggression: Testing the Sensitivity to the Environment

The aim of the study was to explore the possible vulnerability (diathesis-stress), susceptibility (differential susceptibility), or vantage (vantage sensitivity) properties of COMT gen Val158Met polymorphism to adverse and favorable parenting styles from both parents in relation to children's reactive and proactive aggressive behavior. Within 279 eight-year-old children (125 girls and 154 boys) from Spain, reactive and proactive aggressive behavior was measured through the "Reactive and Proactive Questionnaire" (RPQ). Saliva samples were collected to genotype for the COMT Val158Met polymorphism via real-time PCR. Finally, parenting styles were assessed using the "Parenting Styles and Dimensions Questionnaire" (PSDQ). The results revealed that for boys, the Met allele was a vulnerability factor for proactive aggression in response to low-authoritative parenting from the father. For girls, it was the Val allele, the vulnerability variable to the high authoritarian style of the father, and the susceptibility factor to the authoritative style of the mother over proactive aggression. The results are discussed, considering possible sex differences. Our results indicate that the COMT Val158Met polymorphism is a biological variable that confers greater sensitivity to the environment.

Association Between the rs4680 Polymorphism of the COMT Gene and Personality Traits among Combat Sports Athletes

Physical performance has been the focus of studies examining genetic influences in martial arts. There has been little quantitative analysis of the interaction between psychological traits and gene variants in athletes. This study aimed to determine whether the rs4680 polymorphism of the COMT gene (catechol-O-methyltransferase) was linked to other sports phenotypes such as temperament, mental toughness, and stress tolerance. In our study, we concentrated on the case-control analysis of athletes in the aspect of their personality traits in association with the COMT gene polymorphism. Participants comprised 258 combat sports athletes and 278 healthy male individuals as a control group. Psychometric properties were assessed with the Revised Temperament and Character Inventory (TCI-R). COMT polymorphism testing was performed using real-time PCR. We found a statistically significant effect of a complex factor COMT rs4680 genotype with combat athletes/controls and novelty seeking (F2,530 = 5.958, p = 0.0028, η2 = 0.022), self-management (F2,530 = 6.772, p = 0.0012, η2 = 0.025), and with self-transcendence skills (F2,530 = 9.387, p = 0.00009, η2 = 0.034). The results are important for encouraging further studies on the genetic makeup of athletes in conjunction with personality traits. Due to the multigene and multifactorial nature of determinants of sports predispositions, we propose to take into account also other features, especially when studying genes related to cerebral neurotransmission. It is a holistic departure, and it clearly illustrates the relationship between the given characteristics of an athlete.

Effects of childhood trauma on aggressive behaviors and hippocampal function: the modulation of COMT haplotypes

Background

Aggression is a commonly hostile behavior linked to the hippocampal activity. Childhood trauma (CT) exposure has been associated with altered sensitization of the hypothalamic-pituitary-adrenal (HPA) axis and hippocampal volume，which could increase violent aggressive behaviors. Additionally, Catechol-O-methyltransferase (COMT), the major dopamine metabolism enzyme, is implicated in stress responsivity, including aggression. Hence, CT exposure may affect aggression through the effect on the hippocampal function, which might also be modulated by the COMT variations.

Objectives

This study examined whether both CT and haplotypes of COMT moderate hippocampal function and thus affect human aggressive behavior.

Methods

We obtained bilateral hippocampal functional connectivity maps using resting state functional magnetic resonance imaging (MRI) data. COMT haplotype estimation was performed using Haploview 4.2 and PHASE 2.1. Then we constructed a moderated mediation model to study the effect of the CTQ × COMT on aggressive behavior.

Results

Three major haplotypes were generated from thirteen single nucleotide polymorphisms (SNPs) within the COMT gene and formed three haplotypes corresponding to high, medium, and low enzymatic activity of COMT. The results showed interactive relationships between the Childhood Trauma Questionnaire (CTQ) and COMT with respect to the functional connectivity (FC) of the bilateral hippocampus (HIP)-orbital frontal cortex (OFC). Specifically, CT experience predicted lower negative HIP-OFC coupling in the APS and HPS haplotypes corresponding to the medium and high enzymatic activity of COMT, but greater FC in the LPS haplotypes corresponding to the low enzymatic activity. We also observed a conditional mediation effect of the right HIP-OFC coupling in the link between COMT and aggressive behavior that was moderated by CT experience.

Conclusions

These results suggest that CT and COMT have a combined effect on aggressive behavior through hippocampal function. This mediation analysis sheds light on the influence of childhood experience on aggressive behavior in different genetic backgrounds.

COMT Val158Met Affects the Analgesic Response to Acupuncture Among Cancer Survivors With Chronic Pain

Catechol-O-methyltransferase (COMT) is the major enzyme involved in the catabolism of dopamine, a neurotransmitter in the brain's reward system. The common COMT polymorphism Val158Met (rs4680 G>A) modulates pain response to opioids through a reward-motivated mechanism; however, its role in nonpharmacological pain medicine has not been clinically characterized. We genotyped 325 participants from a randomized controlled trial of cancer survivors with chronic musculoskeletal pain. We found that carrying methionine at position 158 (158Met) of COMT, encoded by the A allele, significantly increased the analgesic response to electroacupuncture (74% vs 50%; odds ratio [OR]: 2.79; 95% confidence interval [CI]: 1.31, 6.05; P < .01), but not to auricular acupuncture (68% vs 60%; OR: 1.43; 95% CI: .65, 3.12; P = .37) or usual care (24% vs 18%; OR: 1.46; 95% CI: .38, 7.24; P = .61) compared to Val/Val. These findings raise the possibility that COMT Val158Met might be an important predictor of analgesic response to electroacupuncture, providing novel insights into precision nonpharmacologic pain management tailored to individual genetic backgrounds. PERSPECTIVE: This work suggests the modulating effects of the polymorphism in COMT Val158Met on the response to acupuncture. Further research needs to validate these findings, increase the mechanistic understanding of acupuncture, and guide further development of acupuncture as a precision pain management strategy.

The COMT gene modulates the relationship between bilingual adaptation in executive function and decision-making: an EEG study

Bilingual adaptive control mechanisms appear to be linked to congenital genetic factors such as dopamine (DA) genes. However, it is unclear as to whether acquired cognitive exercise can vanquish innate influences that allow bilingual executive advantages to be shown in other cognitive areas. In the present study, we examine the relationship between gene-dependent executive control and decision-making by targeting the enzyme catecholamine-O-methyltransferase (COMT) and employing electroencephalography (EEG). Chinese-English bilinguals (N = 101) participated in a language switching task and the Iowa Gambling Task (IGT). The findings showed that COMT Val158Met polymorphism played a complex role in decision-making and bilingual executive control processing: Bilinguals with Valine (Val) homozygotes had poorer performance in the IGT, while Methionine (Met) carriers had larger switch costs in the language switching task. Second, the cross-task relationships varied among bilinguals with different COMT genotypes: Bilinguals with Met allele genotypes showed larger switch costs and better performance on the IGT. These findings suggest that bilinguals who carry Met allele are equipped with more efficient adaptive mechanisms of executive functions that are generalized to other cognitive domains.

Supplementary Information

The online version contains supplementary material available at 10.1007/s11571-022-09867-2.

Drosophila mutants lacking the glial neurotransmitter-modifying enzyme Ebony exhibit low neurotransmitter levels and altered behavior

Inhibitors of enzymes that inactivate amine neurotransmitters (dopamine, serotonin), such as catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO), are thought to increase neurotransmitter levels and are widely used to treat Parkinson's disease and psychiatric disorders, yet the role of these enzymes in regulating behavior remains unclear. Here, we investigated the genetic loss of a similar enzyme in the model organism Drosophila melanogaster. Because the enzyme Ebony modifies and inactivates amine neurotransmitters, its loss is assumed to increase neurotransmitter levels, increasing behaviors such as aggression and courtship and decreasing sleep. Indeed, ebony mutants have been described since 1960 as "aggressive mutants," though this behavior has not been quantified. Using automated machine learning-based analyses, we quantitatively confirmed that ebony mutants exhibited increased aggressive behaviors such as boxing but also decreased courtship behaviors and increased sleep. Through tissue-specific knockdown, we found that ebony's role in these behaviors was specific to glia. Unexpectedly, direct measurement of amine neurotransmitters in ebony brains revealed that their levels were not increased but reduced. Thus, increased aggression is the anomalous behavior for this neurotransmitter profile. We further found that ebony mutants exhibited increased aggression only when fighting each other, not when fighting wild-type controls. Moreover, fights between ebony mutants were less likely to end with a clear winner than fights between controls or fights between ebony mutants and controls. In ebony vs. control fights, ebony mutants were more likely to win. Together, these results suggest that ebony mutants exhibit prolonged aggressive behavior only in a specific context, with an equally dominant opponent.

Point-of-Care Testing of Enzyme Polymorphisms for Predicting Hypnotizability and Postoperative Pain

Hypnotizability is a stable trait that moderates the benefit of hypnosis for treating pain, but limited availability of hypnotizability testing deters widespread use of hypnosis. Inexpensive genotyping of four single-nucleotide polymorphisms in the catechol-o-methyltransferase (COMT) gene was performed using giant magnetoresistive biosensors to determine if hypnotizable individuals can be identified for targeted hypnosis referrals. For individuals with the proposed optimal COMT diplotypes, 89.5% score highly on the Hypnotic Induction Profile (odds ratio, 6.12; 95% CI, 1.26-28.75), which identified 40.5% of the treatable population. Mean hypnotizability scores of the optimal group were significantly higher than the total population (P = 0.015; effect size = 0.60), an effect that was present in women (P = 0.0015; effect size = 0.83), but not in men (P = 0.28). In an exploratory cohort, optimal individuals also reported significantly higher postoperative pain scores (P = 0.00030; effect size = 1.93), indicating a greater need for treatment.

Dopamine Dynamics and Neurobiology of Non-Response to Antipsychotics, Relevance for Treatment Resistant Schizophrenia: A Systematic Review and Critical Appraisal

Treatment resistant schizophrenia (TRS) is characterized by a lack of, or suboptimal response to, antipsychotic agents. The biological underpinnings of this clinical condition are still scarcely understood. Since all antipsychotics block dopamine D2 receptors (D2R), dopamine-related mechanisms should be considered the main candidates in the neurobiology of antipsychotic non-response, although other neurotransmitter systems play a role. The aims of this review are: (i) to recapitulate and critically appraise the relevant literature on dopamine-related mechanisms of TRS; (ii) to discuss the methodological limitations of the studies so far conducted and delineate a theoretical framework on dopamine mechanisms of TRS; and (iii) to highlight future perspectives of research and unmet needs. Dopamine-related neurobiological mechanisms of TRS may be multiple and putatively subdivided into three biological points: (1) D2R-related, including increased D2R levels; increased density of D2Rs in the high-affinity state; aberrant D2R dimer or heteromer formation; imbalance between D2R short and long variants; extrastriatal D2Rs; (2) presynaptic dopamine, including low or normal dopamine synthesis and/or release compared to responder patients; and (3) exaggerated postsynaptic D2R-mediated neurotransmission. Future points to be addressed are: (i) a more neurobiologically-oriented phenotypic categorization of TRS; (ii) implementation of neurobiological studies by directly comparing treatment resistant vs. treatment responder patients; (iii) development of a reliable animal model of non-response to antipsychotics.

Genetic profile for dopamine signaling predicts brain functional reactivity to repetitive transcranial magnetic stimulation

Research integrating molecular and imaging data provides important insights into how the genetic profile associated with dopamine signaling influences inter-individual differences in brain functions. However, the effects of genetic variations in dopamine signaling on the heterogeneity of brain changes induced by repetitive transcranial magnetic stimulation (rTMS) still remain unclear. The current study examined the composite effects of genetic variations in dopamine-related genes on rTMS-induced brain responses in terms of the functional network connectivity and working memory performance. Healthy individuals (n = 30) participated in a randomized, double-blind, sham-controlled study with a crossover design of five consecutive days where active rTMS or sham stimulation sessions were administered over the left dorsolateral prefrontal cortex (DLPFC) of the brain. Participants were mostly women (n = 29) and genotyped for polymorphisms in the catechol-O-methyltransferase and D2 dopamine receptor genes and categorized according to their genetic composite scores: high vs. low dopamine signaling groups. Pre- and post-intervention data of resting-state functional magnetic resonance imaging and working memory performance were obtained from 27 individuals with active rTMS and 30 with sham stimulation sessions. The mean functional connectivity within the resting-state networks centered on the DLPFC increased in the high dopamine signaling group. Working memory performance also improved with rTMS in the high dopamine signaling group compared to that in the low dopamine signaling group. The present results suggest that genetic predisposition to higher dopamine signaling may be a promising neurobiological predictor for rTMS effects on cognitive enhancement.Trial registration: ClinicalTrials.gov (NCT02932085).

The molecular genetic basis of creativity: a mini review and perspectives

Although creativity is one of the defining features of human species, it is just the beginning of an ambitious attempt for psychologists to understand its genetic basis. With ongoing efforts, great progress has been achieved in molecular genetic studies of creativity. In this mini review, we highlighted recent molecular genetic findings for both domain-general and domain-specific creativity, and provided some perspectives for future studies. It is expected that this work will provide an update on the knowledge regarding the molecular genetic basis of creativity, and contribute to the further development of this field.

Catechol-O-methyltransferase Inhibitors from Calendula officinalis Leaf

Calendula officinalis is commonly known as marigold and its flowers are used in herbal medicines, cosmetics, perfumes, dyes, pharmaceutical preparations, and food products. However, the utility of its leaves has not been studied in depth. The purpose of the present study was to identify the major compounds in C. officinalis leaves and to determine the inhibitory properties of the isolated compounds toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression. We isolated and identified ten compounds, including two phenylpropanoids and seven flavonoids, from C. officinalis leaf extracts, of which four flavonoids were identified from C. officinalis leaves for the first time. Eight compounds exhibited COMT inhibitory activities with IC₅₀ values of less than 100 μM. Our results indicate that compounds in C. officinalis leaves are potentially effective for preventing Parkinson's disease and depression. Thus, C. officinalis leaves may hold promise as dietary supplements.

Working memory dysfunction in fibromyalgia is associated with genotypes of the catechol- O-methyltransferase gene: an event-related potential study

Recent findings have associated different COMT genotypes with working memory capacity in patients with fibromyalgia. Although it is thought that the COMT gene may influence neural correlates (P2 and P3 ERP components) underlying working memory impairment in this chronic-pain syndrome, it has not yet been explored. Therefore, the aim of the present research was to investigate the potential effect of the COMT gene in fibromyalgia patients on ERP working memory indices (P2 and P3 components). For this purpose, 102 participants (51 patients and 51 healthy control participants) took part in the experiment. Event-related potentials and behavioral responses were recorded while participants performed a spatial n-back task. Participants had to decide if the stimulus coincided or not in the same location as the one presented one (1-back condition) or two (2-back condition) trials before. Genotypes of the COMT gene were determined through a saliva sample from all participants. Present results significantly showed lower working memory performance (p < 0.05) in patients with fibromyalgia as compared to control participants (higher rate of errors and slower reaction times). At neural level, we found that patients exhibited enhanced frontocentral and parieto-occipital P2 amplitudes compared to control participants (p < 0.05). Interestingly, we also observed that only fibromyalgia patients carrying the Val/Val genotype of the COMT gene showed higher frontocentral P2 amplitudes than control participants (p < 0.05). Current results (behavioral outcomes and P2 amplitudes) confirmed the presence of an alteration in working memory functioning in fibromyalgia. The enhancement of frontocentral P2 could be reflecting that these patients would manifest an inefficient way of activating executive attention processes, in carriers of the Val/Val genotype of COMT. To our knowledge, the present findings are the first linking neural indices of working memory dysfunctions and COMT genotypes in fibromyalgia. Applying a subgroup of patient's strategy based on this genetic marker could be useful to establish more tailored therapeutical approaches.

Pramipexole modulates fronto-subthalamic pathway in sequential working memory

Brain dopamine may regulate the ability to maintain and manipulate sequential information online. However, the precise role of dopamine remains unclear. This pharmacological fMRI study examined whether and how the dopamine D2/3 receptor agonist pramipexole modulates fronto-subthalamic or fronto-striatal pathways during sequential working memory. This study used a double-blind, randomized crossover design. Twenty-two healthy male volunteers completed a digit ordering task during fMRI scanning after receiving a single oral dose of 0.5-mg pramipexole or placebo. The pramipexole effects on task performance, regional activity, activity pattern similarity, and functional connectivity were analyzed. Pramipexole impaired task performance, leading to less accurate and slower responses in the digit ordering task. Also, it downregulated the maintenance-related subthalamic and dorsolateral prefrontal activity, increasing reaction times for maintaining sequences. In contrast, pramipexole upregulated the manipulation-related subthalamic and dorsolateral prefrontal activity, increasing reaction time costs for manipulating sequences. In addition, it altered the dorsolateral prefrontal activity pattern similarity and fronto-subthalamic functional connectivity. Finally, pramipexole reduced maintenance-related striatal activity, which did not affect the behavior. This study confirms the role of the fronto-subthalamic pathway in sequential working memory. Furthermore, it shows that D2 transmission can regulate sequential working memory by modulating the fronto-subthalamic pathway.

Blunt dopamine transmission due to decreased GDNF in the PFC evokes cognitive impairment in Parkinson's disease

Studies have found that the absence of glial cell line-derived neurotrophic factor may be the primary risk factor for Parkinson's disease. However, there have not been any studies conducted on the potential relationship between glial cell line-derived neurotrophic factor and cognitive performance in Parkinson's disease. We first performed a retrospective case-control study at the Affiliated Hospital of Xuzhou Medical University between September 2018 and January 2020 and found that a decreased serum level of glial cell line-derived neurotrophic factor was a risk factor for cognitive disorders in patients with Parkinson's disease. We then established a mouse model of Parkinson's disease induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and analyzed the potential relationships among glial cell line-derived neurotrophic factor in the prefrontal cortex, dopamine transmission, and cognitive function. Our results showed that decreased glial cell line-derived neurotrophic factor in the prefrontal cortex weakened dopamine release and transmission by upregulating the presynaptic membrane expression of the dopamine transporter, which led to the loss and primitivization of dendritic spines of pyramidal neurons and cognitive impairment. In addition, magnetic resonance imaging data showed that the long-term lack of glial cell line-derived neurotrophic factor reduced the connectivity between the prefrontal cortex and other brain regions, and exogenous glial cell line-derived neurotrophic factor significantly improved this connectivity. These findings suggested that decreased glial cell line-derived neurotrophic factor in the prefrontal cortex leads to neuroplastic degeneration at the level of synaptic connections and circuits, which results in cognitive impairment in patients with Parkinson's disease.

Are COMT Val158Met (rs4680), DRD2 TaqIA (rs1800497), and BDNF Val66Met (rs6265) polymorphisms associated with executive functions performance at rest and during physical exercise?

Executive functions (EFs) encompass a wide array of cognitive processes, which appear to be influenced by genetic variants of the COMT, DRD2/ANKK1, and BDNF polymorphisms. The present study aimed to investigate whether COMT Val158Met (rs4680), DRD2/ANKK1 (rs1800497), and BDNF Val66Met (rs6265) polymorphisms were associated with EFs assessed at rest and during moderate acute physical exercise. Sixty physically active individuals underwent four laboratory visits. First, they filled out the pre-exercise survey, researchers collected their anthropometric data, and then performed a maximal cardiopulmonary exercise test. In the second and third sessions, participants performed EFs test in a randomized order: while the individual was seated on a cycle ergometer without pedaling (i.e., rest condition); and during physical exercise (pedaling for 30 minutes at moderate intensity before starting the EFs test during exercising). On the fourth day, blood samples were drawn. Our results showed that the response time of the COMT Val homozygotes group was significantly shorter than the COMT Met-carrier group [t(39.78) = 2.13, p = .039,d = 0.56] at rest condition. No significant association was found for the other analyses (DRD2/ANKK1 and BDNF). In conclusion, the present study suggests that COMT Val158Met (rs4680) polymorphisms may be associated with EFs at rest condition. However, further studies are needed to validate this association.

Cognitive performance, creativity and stress levels of neurotypical young adults under different white noise levels

Noise is often considered a distractor; however recent studies suggest that sub-attentive individuals or individuals diagnosed with attention deficit hyperactivity disorder can benefit from white noise to enhance their cognitive performance. Research regarding the effect of white noise on neurotypical adults presents mixed results, thus the implications of white noise on the neurotypical population remain unclear. Thus, this study investigates the effect of 2 white noise conditions, white noise level at 45 dB and white noise level at 65 dB, on the cognitive performance, creativity, and stress levels of neurotypical young adults in a private office space. These conditions are compared to a baseline condition where participants are exposed to the office ambient noise. Our findings showed that the white noise level at 45 dB resulted in better cognitive performance in terms of sustained attention, accuracy, and speed of performance as well as enhanced creativity and lower stress levels. On the other hand, the 65 dB white noise condition led to improved working memory but higher stress levels, which leads to the conclusion that different tasks might require different noise levels for optimal performance. These results lay the foundation for the integration of white noise into office workspaces as a tool to enhance office workers’ performance.

A mechanistic model of ADHD as resulting from dopamine phasic/tonic imbalance during reinforcement learning

Attention deficit hyperactivity disorder (ADHD) is the most common neurodevelopmental disorder in children. Although the involvement of dopamine in this disorder seems to be established, the nature of dopaminergic dysfunction remains controversial. The purpose of this study was to test whether the key response characteristics of ADHD could be simulated by a mechanistic model that combines a decrease in tonic dopaminergic activity with an increase in phasic responses in cortical-striatal loops during learning reinforcement. To this end, we combined a dynamic model of dopamine with a neurocomputational model of the basal ganglia with multiple action channels. We also included a dynamic model of tonic and phasic dopamine release and control, and a learning procedure driven by tonic and phasic dopamine levels. In the model, the dopamine imbalance is the result of impaired presynaptic regulation of dopamine at the terminal level. Using this model, virtual individuals from a dopamine imbalance group and a control group were trained to associate four stimuli with four actions with fully informative reinforcement feedback. In a second phase, they were tested without feedback. Subjects in the dopamine imbalance group showed poorer performance with more variable reaction times due to the presence of fast and very slow responses, difficulty in choosing between stimuli even when they were of high intensity, and greater sensitivity to noise. Learning history was also significantly more variable in the dopamine imbalance group, explaining 75% of the variability in reaction time using quadratic regression. The response profile of the virtual subjects varied as a function of the learning history variability index to produce increasingly severe impairment, beginning with an increase in response variability alone, then accumulating a decrease in performance and finally a learning deficit. Although ADHD is certainly a heterogeneous disorder, these results suggest that typical features of ADHD can be explained by a phasic/tonic imbalance in dopaminergic activity alone.

Task-level value affects trial-level reward processing

Despite disagreement about how anterior cingulate cortex (ACC) supports decision making, a recent hypothesis suggests that activity in this region is best understood in the context of a task or series of tasks. One important task-level variable is average reward because it is both a known driver of effortful behaviour and an important determiner of the tasks in which we choose to engage. Here we asked how average task value affects reward-related ACC activity. To answer this question, we measured a reward-related signal said to be generated in ACC called the reward positivity (RewP) while participants gambled in three tasks of differing average value. The RewP was reduced in the high-value task, an effect that was not explainable by either reward magnitude or outcome expectancy. This result suggests that ACC does not evaluate outcomes and cues in isolation, but in the context of the value of the current task.

Thermostability and catechol-O-methyltransferase inhibitory activity of acylated anthocyanins from purple yam

The thermostability of purple yam was investigated to be used as natural colorants. In addition, the inhibitory properties of purple yam and its isolated anthocyanins toward human catechol-O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression, were also investigated. The thermostability of purple yam was higher than that of the reference samples (purple sweet potato and purple potato). Quantitative HPLC analysis revealed that alatanin A (2) contributed to the thermostability of purple yam. Methanol extracts of purple yam exhibited the highest COMT inhibitory activity of the tested samples. Alatanin D (1) showed the highest inhibitory activity of the anthocyanins in purple yam (IC50 19 µM). This study revealed the thermostability and COMT inhibitory activity of purple yam and may lead to its use not only as a thermostable natural source of colorants, but also for the prevention and treatment of Parkinson's disease and depression.

Toxoplasma gondii Seropositivity Interacts with Catechol-O-methyltransferase Val105/158Met Variation Increasing the Risk of Schizophrenia

Schizophrenia is a heterogeneous and severe psychotic disorder. Epidemiological findings have suggested that the exposure to infectious agents such as Toxoplasma gondii (T. gondii) is associated with an increased risk for schizophrenia. On the other hand, there is evidence involving the catechol-O-methyltransferase (COMT) Val105/158Met polymorphism in the aetiology of schizophrenia since it alters the dopamine metabolism. A case−control study of 141 patients and 142 controls was conducted to analyse the polymorphism, the prevalence of anti-T. gondii IgG, and their interaction on the risk for schizophrenia. IgG were detected by ELISA, and genotyping was performed with TaqMan Real-Time PCR. Although no association was found between any COMT genotype and schizophrenia, we found a significant association between T. gondii seropositivity and the disorder (χ2 = 11.71; p-value < 0.001). Furthermore, the risk for schizophrenia conferred by T. gondii was modified by the COMT genotype, with those who had been exposed to the infection showing a different risk compared to that of nonexposed ones depending on the COMT genotype (χ2 for the interaction = 7.28, p-value = 0.007). This study provides evidence that the COMT genotype modifies the risk for schizophrenia conferred by T. gondii infection, with it being higher in those individuals with the Met/Met phenotype, intermediate in heterozygous, and lower in those with the Val/Val phenotype.

The correlation between genetic factors and freezing of gait in patients with Parkinson's disease

BACKGROUND

Clinical-related risk factors to freezing of gait (FOG) in Parkinson's disease (PD) have been identified. Still, the influence of genetic variations on the FOG occurrence has been poorly studied thus far.

AIM

We aimed to evaluate the association of six selected polymorphisms of DRD2, ANKK1, and COMT genes with the FOG occurrence and explore the influence of ANNK1/DRD2 haplotypes on the onset of FOG in the group of PD patients.

METHOD

PD patients (n = 234), treated with levodopa for at least two years, were genotyped for the rs4680 in COMT, rs6277, rs1076560, and rs2283265 in DRD2, and rs1800497 and rs2734849 polymorphisms in ANKK1 genes. FOG was evaluated by posing a direct question. In addition, a comprehensive set of clinical scales was applied to all patients.

RESULTS

FOG occurred in 132 (56.4%) PD patients in our cohort. Freezers were younger at PD onset, had longer disease duration, used higher levodopa daily doses and dopaminergic agents, and had higher motor and non-motor scales scores than non-freezers. FOG was more frequent among AA rs4680 COMT carriers than AG and GG rs4680 COMT carriers. Independent predictors of FOG were: disease duration of more than ten years, levodopa daily dose higher than 500 mg/day, motor status, and COMT AA genotype. AGGAA and GGAAA haplotypes were revealed as protective and vulnerability factors for FOG occurrence.

CONCLUSION

In addition to previously identified disease- and therapy-related risk factors, our results suggested a possible contribution of dopamine-related genes to the FOG occurrence.

Correlation Between Resting Theta Power and Cognitive Performance in Patients With Schizophrenia

Objective

Schizophrenia is a mental disorder that is characterized by progressive cognitive impairment. Objective measures of cognitive function may provide reliable neurobiomarkers for patients with schizophrenia. The goal of the current work is to explore the correlation between resting theta power and cognitive performance in patients with schizophrenia.

Methods

Twenty-two patients with schizophrenia and 23 age-, sex-, and education-matched healthy controls were included in this study. The MATRICS Consensus Cognitive Battery (MCCB) was used for cognitive evaluation and the Positive and Negative Syndrome Scale (PANSS) for evaluation of clinical symptoms. EEGs were acquired in the resting state with closed and opened eyes. Between the two groups, we compared the relative theta power and examined their relationship with cognitive performance.

Results

Compared to healthy controls, patients with schizophrenia showed significantly higher theta power, both with eyes closed and open (P < 0.05). When the eyes were open, negative correlations were found in patients with schizophrenia between theta power in the central and parietal regions with processing speed scores, and between the theta power of the Pz electrode and verbal learning and reasoning and problem-solving scores (r ≥ −0.446). In the control group, theta power over the Fz electrode was negatively correlated with processing speed (r = −0.435).

Conclusions

Our findings showed that theta activity increased in certain brain regions during resting state in schizophrenia. Negative associations between resting theta power (increased) over the parietal-occipital regions with MCCB domains scores (decreased) suggest that altered theta activity can be used as a neurobiological indicator to predict cognitive performance.

Role of Catechol-O-methyltransferase Val158Met Polymorphism on Transcranial Direct Current Stimulation in Swallowing

Transcranial direct current stimulation (tDCS) is one of the latest post-stroke dysphagia treatment modalities, and the effect of tDCS is known to be affected by various factors including genetic polymorphisms. However, the role of catechol-O-methyltransferase (COMT) polymorphisms on tDCS in swallowing is unclear. In this prospective pilot study, we aim to explore the effect of tDCS on the swallowing cortex and subsequent swallowing motor function according to COMT polymorphism. Twenty-four healthy participants received either anodal tDCS or sham mode tDCS on the mylohyoid motor cortex at random order, after inhibitory repetitive transcranial magnetic stimulation (rTMS) for preconditioning. The primary outcome was the changes of mylohyoid-motor-evoked potentials (MH-MEP) amplitude in each COMT polymorphism group, from the post-inhibitory rTMS baseline state to immediate, 30, and 60 min after tDCS. The secondary outcomes were the changes in swallowing function. The results showed that COMT Val/Val polymorphism showed improvement across time in the MH-MEP amplitudes and triggering time of swallowing after tDCS, whereas COMT Met carrier group did not show significant changes of MH-MEP or swallowing function across time. This therapeutic response variability of tDCS in the mylohyoid motor system according to COMT polymorphism support the importance of genetic analysis in individualized dysphagia treatment.

Influence of Catechol-O-Methyltransferase Gene Polymorphism on the Correlation between Alexithymia and Hypervigilance to Pain

The psychological characteristic of having difficulty expressing emotions, known as alexithymia, is associated with hypervigilance to pain and is considered one of the risk factors for chronic pain. The correlation between alexithymia and hypervigilance to pain can be observed even in healthy individuals. However, the factors influencing this correlation remain unknown. We explored the dopamine system, which is known to be involved in emotion and pain. The dopamine-degrading enzyme catechol-O-methyltransferase (COMT) has a genetic polymorphism known to influence dopamine metabolism in the prefrontal cortex. COMT polymorphism reportedly affects various aspects of pain and increases pain sensitivity in Met allele carriers. Therefore, we investigated whether the correlation between alexithymia and hypervigilance to pain is influenced by COMT polymorphism in healthy individuals. The results revealed a significant positive correlation between the "difficulty describing feelings" of the 20-item Toronto Alexithymia Scale and the "attention to changes in pain" of the pain vigilance and awareness questionnaire in COMT Met carriers but not in Val/Val individuals. This finding suggests that the correlation between alexithymia and hypervigilance to pain is influenced by COMT polymorphism.

Dopamine, Cognitive Flexibility, and IQ: Epistatic Catechol-O-MethylTransferase:DRD2 Gene-Gene Interactions Modulate Mental Rigidity

Cognitive flexibility has been hypothesized to be neurochemically rooted in dopamine neurotransmission. Nonetheless, underpowered sample sizes and contradictory meta-analytic findings have obscured the role of dopamine genes in cognitive flexibility and neglected potential gene-gene interactions. In this largest neurocognitive-genetic study to date (n = 1400), single nucleotide polymorphisms associated with elevated prefrontal dopamine levels (catechol-O-methyltransferase; rs4680) and diminished striatal dopamine (C957T; rs6277) were both implicated in Wisconsin Card Sorting Test performance. Crucially, however, these genetic effects were only evident in low-IQ participants, suggesting high intelligence compensates for, and eliminates, the effect of dispositional dopamine functioning on flexibility. This interaction between cognitive systems may explain and resolve previous empirical inconsistencies in highly educated participant samples. Moreover, compensatory gene-gene interactions were discovered between catechol-O-methyltransferase and DRD2, such that genotypes conferring either elevated prefrontal dopamine or diminished striatal dopamine-via heightened striatally concentrated D2 dopamine receptor availability-are sufficient for cognitive flexibility, but neither is necessary. The study has therefore revealed a form of epistatic redundancy or substitutability among dopamine systems in shaping adaptable thought and action, thus defining boundary conditions for dopaminergic effects on flexible behavior. These results inform theories of clinical disorders and psychopharmacological interventions and uncover complex fronto-striatal synergies in human flexible cognition.

Reading abilities and dopamine D2/D3 receptor availability: An inverted U-shaped association in subjects with schizophrenia

Reading impairments are prominent trait-like features of cognitive deficits in schizophrenia, predictive of overall cognitive functioning and presumably linked to dopaminergic abnormalities. To evaluate this, we used ¹⁸F-fallypride PET in 19 healthy and 21 antipsychotic-naïve schizophrenia subjects and correlated dopamine receptor binding potentials in relevant AFNI-derived regions and voxelwise with group performance on WRAT4 single-word reading subtest. Healthy subjects' scores were positively and linearly associated with D₂/D₃ receptor availability in the rectus, orbital and superior frontal gyri, fusiform and middle temporal gyri, as well as middle occipital gyrus and precuneus, all predominantly in the left hemisphere and previously implicated in reading, hence suggesting that higher dopamine receptor density is cognitively advantageous. This relationship was weakened in schizophrenia subjects and in contrast to healthy participants followed an inverted U-shaped curve both in the cortex and dorsal striatum, indicating restricted optimal range of dopamine D₂/D₃ receptor availability for cognitive performance in schizophrenia.

Harsh parenting and non-suicidal self-injury in adolescence: the mediating effect of depressive symptoms and the moderating effect of the COMT Val158Met polymorphism

BACKGROUND

Previous studies have suggested that negative parenting environments, especially harsh parenting, are a specific risk factor for non-suicidal self-injury (NSSI). However, the potential mechanism between harsh parenting and NSSI has not been explored. Based on the experiential avoidance model and empirical research, we aimed to examine whether depressive symptoms are a mediator between harsh parenting and NSSI. Moreover, the catechol-O-methyltransferase (COMT) Val158Met polymorphism related to depressive symptoms may also exert a moderating effect on NSSI; thus, the interaction between harsh parenting and COMT was also considered in our study.

METHODS

A total of 373 junior high school students were recruited for the study by using a longitudinal design. The adolescents answered self-report questionnaires and provided saliva samples for DNA genotyping.

RESULTS

The results revealed that harsh parenting was positively associated with NSSI after 24 months, and this association was mediated by depressive symptoms. Moreover, the moderating role of COMT in the direct and indirect effects of harsh parenting on NSSI was observed only among adolescents with two Val alleles and the relationship was not significant for Met carriers.

CONCLUSIONS

Genetic variations of COMT Val158Met may be a critical candidate in understanding the development of depression and NSSI. We conclude that Val homozygotes of the COMT Val158Met polymorphism play a role in susceptibility to both depressive symptoms and NSSI.

A common polymorphism in the dopamine transporter gene predicts working memory performance and in vivo dopamine integrity in aging

Dopamine (DA) integrity is suggested as a potential cause of individual differences in working memory (WM) performance among older adults. Still, the principal dopaminergic mechanisms giving rise to WM differences remain unspecified. Here, 61 single-nucleotide polymorphisms, located in or adjacent to various dopamine-related genes, were assessed for their links to WM performance in a sample of 1313 adults aged 61-80 years from the Berlin Aging Study II. Least Absolute Shrinkage and Selection Operator (LASSO) regression was conducted to estimate associations between polymorphisms and WM. Rs40184 in the DA transporter gene, SLC6A3, showed allelic group differences in WM, with T-carriers performing better than C homozygotes (p<0.01). This finding was replicated in an independent sample from the Cognition, Brain, and Aging study (COBRA; baseline: n = 181, ages: 64-68 years; 5-year follow up: n = 129). In COBRA, in vivo DA integrity was measured with ¹¹C-raclopride and positron emission tomography. Notably, WM as well as in vivo DA integrity was higher for rs40184 T-carriers at baseline (p<0.05 for WM and caudate and hippocampal D2-receptor availability) and at the 5-year follow-up (p<0.05 for WM and hippocampal D2 availability). Our findings indicate that individual differences in DA transporter function contribute to differences in WM performance in old age, presumably by regulating DA availability.

Effect of Catechol-O-Methyltransferase Genotype Polymorphism on Neurological and Psychiatric Disorders: Progressing Towards Personalized Medicine

Different polymorphisms of the catechol-O-methyltransferase (COMT) gene affect the COMT enzyme activity. The COMT enzyme plays a major role in the pathophysiology of various neurological and psychiatric disorders. This review article aims to discuss what recent research has discovered about the association of COMT genotype polymorphism with neurological and psychiatric disorders and the scope for the knowledge to be applied for advancement in therapeutics. We searched PubMed and Google Scholar databases and found 1656 articles. We included observational studies, clinical trials, and meta-analyses in the English language published between 2019 and 2021. We screened the articles based on the title and the abstract and found 26 relevant articles. Diseases or conditions studied primarily were schizophrenia, Parkinson’s disease, Alzheimer’s disease, substance use, and depression. This article highlights how genetics influences the susceptibility of an individual to neurological and psychiatric diseases and the variations in the specific symptoms of those diseases. The review showed that the variability in individual response to therapeutic interventions stems from the gene level. This knowledge can contribute towards the dawn of a new era of personalized medicine.

Evaluation of the Association of COMT Rs4680 Polymorphism with Swimmers' Competitive Performance

Swimmers' competitive performance is a result of complicated interactions between physiological, biochemical, physical and psychological factors, all of which are strongly affected by water. Recently, great attention has been paid to the role of genetic factors such as the catechol-O-methyltransferase gene (COMT) influencing motivation, emotions, stress tolerance, self-control, sleep regulation, pain processing and perception, addictive behaviour and neurodegeneration, which may underlie differences in achieving remarkable results in sports competition. Thus, this study was performed to investigate the association between the COMT Val158Met (rs4680) polymorphism and athletic performance in Caucasian swimmers. A total of 225 swimmers (171 short distance (SDS) and 54 long distance swimmers (LDS)) of national or international competitive standard and 379 unrelated sedentary controls were genotyped using real-time polymerase chain reaction (real-time PCR). We found no significant differences in genotypic or allelic distributions between (1) male and female athletes; (2) SDS and LDS; (3) all athletes and sedentary controls (under codominant, dominant, recessive, and overdominant genetic models). No association was found between the COMT rs4680 polymorphism and elite swimming athlete status of the studied population. However, more replication studies are needed.

Catechol-O-Methyltransferase Inhibitors Isolated From Thai Propolis

Propolis is an aggregate of functional components found in plant resins and has been reported to exhibit a variety of valuable biological activities. This study investigated the inhibitory properties of propolis from Thailand toward human catechol- O-methyltransferase (COMT), a key neurotransmitter involved in Parkinson's disease and depression. Samples collected from Chanthaburi and Chiang Mai exhibited relatively high inhibitory activity against COMT. γ-Mangostin (1) and 6-prenyleriodictyol (3) were identified as COMT inhibitors with IC50 values of 62 and 75 μM, respectively. In an enzyme inhibition assay, 1 exhibited mixed inhibition toward COMT. The results suggest that both 1 and propolis have potential applications in the prevention and treatment of psychological illness.

Role of COMT V158M Polymorphism in the Development of Dystonia after Administration of Antipsychotic Drugs

Antipsychotics (APDs) represent the main pharmacological strategy in the treatment of schizophrenia; however, their administration often may result in severe adverse effects, such as extrapyramidal symptoms. Typically, dystonic movements are considered the result of impaired function and/or abnormalities of dopaminergic neurotransmission/signaling in the basal ganglia. The catechol O-methyltransferase (COMT) gene is located within the 22q11.2 region, and its product is an enzyme involved in transferring a methyl group from S-adenosylmethionine to catecholamines, including dopamine. Studies showed that COMT Val158Met polymorphism modifies enzymatic activity and, consequently, synaptic dopamine concentration in specific brain areas. We identified a patient with 22q11.2 deletion syndrome presenting with cervical and trunk dystonia after paliperidone administration, which persisted even after drug discontinuation. Given the patient’s genetic condition, we hypothesized that the dopaminergic dysfunction had been aggravated by COMT involvement, thus causing dystonia. In line with this hypothesis, we carried out a study on psychiatric patients in chronic treatment with APD to evaluate the distribution of the COMT Val158Met polymorphism and its role in the onset of adverse extrapyramidal symptoms. The study included four patients with dystonia after administration of APDs compared to 17 patients who never presented adverse drug reactions. Our data suggest that the Val/Val and Met/Met polymorphisms of the COMT gene are associated with a protective effect for the development of collateral extrapyramidal symptoms in patients treated with APDs, while the Val/Met genotype could be considered a risk factor for the development of dystonia after APDs administration.

Critical review of the evidence base regarding theories conceptualising the aetiology of psychosis

A critical review of literature related to the aetiology of psychosis was conducted with specific emphasis on genetics. It was found that, although many published articles were retrieved via database searches, the format of the information was disparate in presentation leading to unnecessary inconsistences. This suggests the need for insightful collaboration by authors and standardisation of published articles to prevent academic and specialism barriers remaining as a discouragement to non-specialists wishing to access this information.

Polygenic risk for immuno-metabolic markers and specific depressive symptoms: A multi-sample network analysis study

BACKGROUND

About every fourth patient with major depressive disorder (MDD) shows evidence of systemic inflammation. Previous studies have shown inflammation-depression associations of multiple serum inflammatory markers and multiple specific depressive symptoms. It remains unclear, however, if these associations extend to genetic/lifetime predisposition to higher inflammatory marker levels and what role metabolic factors such as Body Mass Index (BMI) play. It is also unclear whether inflammation-symptom associations reflect direct or indirect associations, which can be disentangled using network analysis.

METHODS

This study examined associations of polygenic risk scores (PRSs) for immuno-metabolic markers (C-reactive protein [CRP], interleukin [IL]-6, IL-10, tumour necrosis factor [TNF]-α, BMI) with seven depressive symptoms in one general population sample, the UK Biobank study (n = 110,010), and two patient samples, the Munich Antidepressant Response Signature (MARS, n = 1058) and Sequenced Treatment Alternatives to Relieve Depression (STAR*D, n = 1143) studies. Network analysis was applied jointly for these samples using fused graphical least absolute shrinkage and selection operator (FGL) estimation as primary analysis and, individually, using unregularized model search estimation. Stability of results was assessed using bootstrapping and three consistency criteria were defined to appraise robustness and replicability of results across estimation methods, network bootstrapping, and samples.

RESULTS

Network analysis results displayed to-be-expected PRS-PRS and symptom-symptom associations (termed edges), respectively, that were mostly positive. Using FGL estimation, results further suggested 28, 29, and six PRS-symptom edges in MARS, STAR*D, and UK Biobank samples, respectively. Unregularized model search estimation suggested three PRS-symptom edges in the UK Biobank sample. Applying our consistency criteria to these associations indicated that only the association of higher CRP PRS with greater changes in appetite fulfilled all three criteria. Four additional associations fulfilled at least two consistency criteria; specifically, higher CRP PRS was associated with greater fatigue and reduced anhedonia, higher TNF-α PRS was associated with greater fatigue, and higher BMI PRS with greater changes in appetite and anhedonia. Associations of the BMI PRS with anhedonia, however, showed an inconsistent valence across estimation methods.

CONCLUSIONS

Genetic predisposition to higher systemic inflammatory markers are primarily associated with somatic/neurovegetative symptoms of depression such as changes in appetite and fatigue, consistent with previous studies based on circulating levels of inflammatory markers. We extend these findings by providing evidence that associations are direct (using network analysis) and extend to genetic predisposition to immuno-metabolic markers (using PRSs). Our findings can inform selection of patients with inflammation-related symptoms into clinical trials of immune-modulating drugs for MDD.

Investigating interactive effects of worry and the catechol-o-methyltransferase gene (COMT) on working memory performance

Extant research indicates that worry is associated with reduced working memory. It remains unclear, however, what mechanisms contribute to impaired performance in worriers. Critically, dopamine in the prefrontal cortex heavily influences the stability of mental representations during working memory tasks, yet no research has probed its role in associations between worry and working memory. To address this gap, the current study was designed to examine the moderating role of dopamine on the association between worry and working memory, using the catechol-o-methyltransferase (COMT) gene as a proxy for basal levels of dopamine. Across four assessments, we examined within- and between-person variation in worry and its interactive effects with COMT to predict working memory performance. Within-person variation in worry interacted with COMT to predict accuracy, such that higher worry across time predicted less accuracy for homozygous Val carriers but not Met carriers. Our findings demonstrate that basal dopamine plays an important role in how increases in worry across time for an individual negatively impact working memory performance.

Neurocognitive subprocesses of working memory performance

Working memory (WM) has been defined as the active maintenance and flexible updating of goal-relevant information in a form that has limited capacity and resists interference. Complex measures of WM recruit multiple subprocesses, making it difficult to isolate specific contributions of putatively independent subsystems. The present study was designed to determine whether neurophysiological indicators of proposed subprocesses of WM predict WM performance. We recruited 200 individuals defined by care-seeking status and measured neural responses using electroencephalography (EEG), while participants performed four WM tasks. We extracted spectral and time-domain EEG features from each task to quantify each of the hypothesized WM subprocesses: maintenance (storage of content), goal maintenance, and updating. We then used EEG measures of each subprocess as predictors of task performance to evaluate their contribution to WM. Significant predictors of WM capacity included contralateral delay activity and frontal theta, features typically associated with maintenance (storage of content) processes. In contrast, significant predictors of reaction time and its variability included contingent negative variation and the P3b, features typically associated with goal maintenance and updating. Broadly, these results suggest two principal dimensions that contribute to WM performance, tonic processes during maintenance contributing to capacity, and phasic processes during stimulus processing that contribute to response speed and variability. The analyses additionally highlight that reliability of features across tasks was greater (and comparable to that of WM performance) for features associated with stimulus processing (P3b and alpha), than with maintenance (gamma, theta and cross-frequency coupling).

Sarcopenia and Neuroscience: Learning to Communicate

In the 1990s and early 2000s, the common definition for sarcopenia was age-related loss of skeletal muscle, and low levels of muscle mass were central to sarcopenia diagnosis. In more recent consensus definitions, however, low muscle strength displaces low muscle mass as a defining feature of sarcopenia. The change stems from growing evidence that muscle weakness is a better predictor of adverse health outcomes (e.g., mobility limitations) than muscle mass. This evidence accompanies an emerging recognition that central neural mechanisms are critical determinants of age-related changes in strength and mobility that can occur independently of variations in muscle mass. However, strikingly little practical attention is typically given to the potential role of the central nervous system in the aetiology or remediation of sarcopenia (i.e., low muscle function). In this article, we provide an overview of some mechanisms that mediate neural regulation of muscle contraction and control, and highlight the specific contributions of neural hypoexcitability, dopaminergic dysfunction, and degradation of functional and structural brain connectivity in relation to sarcopenia. We aim to enhance the lines of communication between the domains of sarcopenia and neuroscience. We believe that appreciation of the neural regulation of muscle contraction and control is fundamental to understanding sarcopenia and to developing targeted therapeutic strategies for its treatment.

The neurochemistry of hypnotic suggestion

A diverse array of studies has been devoted to understanding the neurochemical systems supporting responsiveness to hypnotic suggestions, with implications for experimental and clinical applications of hypnosis. However, this body of research has only rarely been integrated and critically evaluated and the prospects for the reliable pharmacological manipulation of hypnotic suggestibility remain poorly understood. Here we draw on pharmacological, genotyping, neuroimaging, and electrophysiological research to synthesize current knowledge regarding the potential role of multiple widely-studied neurochemicals in response to suggestion. Although we reveal multiple limitations with this body of evidence, we identify converging results implicating different neurochemical systems in response to hypnotic suggestion. We conclude by assessing the extent to which different results align or diverge and outline multiple avenues for future research. Elucidating the neurochemical systems underlying response to suggestion has the potential to significantly advance our understanding of suggestion.

Catechol-O-Methyltransferase Genotype, Frailty, and Gait Speed in a Biracial Cohort of Older Adults

OBJECTIVE

To examine whether the association between dopamine-related genotype and gait speed differs according to frailty status or race.

DESIGN

Cross-sectional population-based study (Cardiovascular Health Study).

SETTING

Multicenter study, four U.S. sites.

PARTICIPANTS

Volunteer community-dwelling adults aged 65 years and older, without evidence of Parkinson's disease (N = 3,744; 71 years; 82% White; 39% male).

MEASUREMENTS

Gait speed (usual pace; m/s), physical frailty (Fried definition), and genetic polymorphism of catechol-O-methyltransferase (COMT; rs4680), an enzyme regulating tonic brain dopamine levels, were assessed. Interaction of COMT by frailty and by race predicting gait speed were tested, and, if significant, analyses were stratified. Multivariable regression models of COMT predicting gait speed were adjusted for demographics and locomotor risk factors. Sensitivity analyses were repeated, stratified by clinical cutoffs of gait speed (0.6 and 1.0 m/s) instead of frailty status.

RESULTS

The interaction of COMT by frailty and COMT by race were P = .02 and P = .01, respectively. Compared with Met/Met (higher dopaminergic signaling), the Val/Val group (lower dopaminergic signaling) walked marginally more slowly in the full cohort (0.87 vs 0.89 m/s; P = .2). Gait speed differences were significant for frail (n = 220; 0.55 vs 0.63 m/s; P = .03), but not for prefrail (n = 1,691; 0.81 vs 0.81 m/s; P = .9) or nonfrail (n = 1,833; 0.98 vs 0.97 m/s; P = .7); results were similar in fully adjusted models. Among frail, associations were similar for Whites and Blacks, with statistical significance for Whites only. Associations stratified by clinical cutoffs of gait speed were not significant.

CONCLUSION

The association of dopamine-related genotype with gait speed is stronger among adults with frailty compared with those without frailty. The potential effects of dopaminergic signaling on preserving physical function in biracial cohorts of frail adults should be further examined.

PET Imaging of Dopamine Neurotransmission During EEG Neurofeedback

Neurofeedback (NFB) is a brain-based training method that enables users to control their own cortical oscillations using real-time feedback from the electroencephalogram (EEG). Importantly, no investigations to date have directly explored the potential impact of NFB on the brain's key neuromodulatory systems. Our study's objective was to assess the capacity of NFB to induce dopamine release as revealed by positron emission tomography (PET). Thirty-two healthy volunteers were randomized to either EEG-neurofeedback (NFB) or EEG-electromyography (EMG), and scanned while performing self-regulation during a single session of dynamic PET brain imaging using the high affinity D2/3 receptor radiotracer, [18F]Fallypride. NFB and EMG groups down-regulated cortical alpha power and facial muscle tone, respectively. Task-induced effects on endogenous dopamine release were estimated in the frontal cortex, anterior cingulate cortex, and thalamus, using the linearized simplified reference region model (LSRRM), which accounts for time-dependent changes in radiotracer binding following task initiation. Contrary to our hypothesis of a differential effect for NFB vs. EMG training, significant dopamine release was observed in both training groups in the frontal and anterior cingulate cortex, but not in thalamus. Interestingly, a significant negative correlation was observed between dopamine release in frontal cortex and pre-to-post NFB change in spontaneous alpha power, suggesting that intra-individual changes in brain state (i.e., alpha power) could partly result from changes in neuromodulatory tone. Overall, our findings constitute the first direct investigation of neurofeedback's effect on the endogenous release of a key neuromodulator, demonstrating its feasibility and paving the way for future studies using this methodology.

Sex moderates the association between the COMT Val158Met single-nucleotide polymorphism and disorderliness facet of novelty seeking

Previous studies have shown inconsistent results regarding the effect of the Val¹⁵⁸Met polymorphism of the catechol-O-methyltransferase (COMT) gene on personality and cognition. Here, nonclinical Caucasian university students of Italian origin were administered the Temperament and Character Inventory-Revised, Tellegen Absorption Scale, Differential Attentional Processes Inventory, and Waterloo-Stanford Group Scale of Hypnotic Susceptibility. We found that the COMT Val¹⁵⁸Met polymorphism was significantly associated with the disorderliness facet of novelty seeking (NS4) and that sex was a moderator of this association. Females with the Met/Met genotype showed higher NS4 scores compared to those with the Val/Met and Val/Val genotypes. No significant genotype effect was found for males. Additionally, we failed to find a significant effect of the COMT gene on attention and hypnotic suggestibility measures. These results provide further evidence for a sex-specific influence on the gene-behaviour associations.

Pharmacodynamic Gene Testing in Prader-Willi Syndrome

Prader-Willi syndrome (PWS) is a rare genetic disorder with a complex neurobehavioral phenotype associated with considerable psychiatric co-morbidity. This clinical case series, for the first time, describes the distribution and frequency of polymorphisms of pharmacodynamic genes (serotonin transporter, serotonin 2A and 2C receptors, catechol-o-methyltransferase, adrenergic receptor 2A, methylene tetrahydrofolate reductase, and human leucocytic antigens) across the two major molecular classes of PWS in a cohort of 33 referred patients who met medical criteria for testing. When results were pooled across PWS genetic subtypes, genotypic and allelic frequencies did not differ from normative population data. However, when the genetic subtype of PWS was examined, there were differences observed across all genes tested that may affect response to psychotropic medication. Due to small sample size, no statistical significance was found, but results suggest that pharmacodynamic gene testing should be considered before initiating pharmacotherapy in PWS. Larger scale studies are warranted.

Effects of childhood trauma experience and COMT Val158Met polymorphism on brain connectivity in a multimodal MRI study

Childhood adversity may act as a stressor to produce a cascade of neurobiological effects that irreversibly alter neural development, setting the stage for developing psychopathology in adulthood. The catechol-O-methyltransferase (COMT) Val158Met polymorphism has received much attention as a candidate gene associated with environmental adversity, modifying risk for psychopathology. In this study, we aim to see how gene × brain × environment models give a more integrative understanding of brain modifications that contribute to predicting psychopathology related to childhood adversity. A large nonclinical sample of young adults completed Childhood Trauma Questionnaire (CTQ), behavioral scores, multimodal magnetic resonance imaging (MRI) scans, and genotyping. We utilized graph-based connectivity analysis in morphometric similarity mapping and resting-state functional MRI to investigate brain alterations. Relationships among COMT genotypes, CTQ score, imaging phenotypes, and behavioral scores were identified by multiple regression and mediation effect analysis. Significant main effect of CTQ score was found in anatomic connectivity of orbitofrontal cortex that was an outstanding mediator supporting the relationship between CTQ score and anxiety/harm-avoiding personality. We also noted the main effect of childhood trauma on reorganization of functional connectivity within the language network. Additionally, we found genotype × CTQ score interactions on functional connectivity of the right frontoparietal network as well as anatomic connectivity of motor and limbic regions. Our data demonstrate childhood adversity and COMT genotypes are associated with abnormal brain connectivity, structurally and functionally. Early identification of individuals at risk, assessment of brain abnormality, and cognitive interventions may help to prevent or limit negative outcomes.

Is impaired dopaminergic function associated with mobility capacity in older adults?

The capacity to move is essential for independence and declines with age. Slow movement speed, in particular, is strongly associated with negative health outcomes. Prior research on mobility (herein defined as movement slowness) and aging has largely focused on musculoskeletal mechanisms and processes. More recent work has provided growing evidence for a significant role of the nervous system in contributing to reduced mobility in older adults. In this article, we report four pieces of complementary evidence from behavioral, genetic, and neuroimaging experiments that, we believe, provide theoretical support for the assertion that the basal ganglia and its dopaminergic function are responsible, in part, for age-related reductions in mobility. We report four a posteriori findings from an existing dataset: (1) slower central activation of ballistic force development is associated with worse mobility among older adults; (2) older adults with the Val/Met intermediate catecholamine-O-methyl-transferase (COMT) genotype involved in dopamine degradation exhibit greater mobility than their homozygous counterparts; (3) there are moderate relationships between performance times from a series of lower and upper extremity tasks supporting the notion that movement speed in older adults is a trait-like attribute; and (4) there is a relationship of functional connectivity within the medial orbofrontal (mOFC) cortico-striatal network and measures of mobility, suggesting that a potential neural mechanism for impaired mobility with aging is the deterioration of the integrity of key regions within the mOFC cortico-striatal network. These findings align with recent basic and clinical science work suggesting that the basal ganglia and its dopaminergic function are mechanistically linked to age-related reductions in mobility capacity.